One method of building radial tires involves the building of a tread band with breaker plies on an assembly drum, and then transferring this tread band by means of a transfer ring to a carcass mounted on an inflatable building drum. An example of such a tire building method and apparatus is shown in U.S. Pat. No. 3,475,254 to V. E. Henley, assigned to the assignee of the present invention. Another example of the transfer ring is shown in U.S. Pat. No. 3,442,746 to M. N. Robertson, also assigned to the assignee of the present invention.
After the tire is built using apparatus such as that shown in the foregoing patents, the common practice has been simply to deflate the building drum and remove the uncured tire band by hand. The operator then usually places the tire band in a cart or another suitable transport or storage apparatus. With the building of larger radial tires, however, such handling of uncured tire bands by hand can be extremely difficult if not impossible, because of their great weight. Also, the handling of heavy, uncured tire bands is an inefficient procedure, because a skilled tire builder's time and energy can be put to better use than in lifting and carrying such tire bands.
A mechanism for removing an uncured tire band from a building drum is shown in U.S. Pat. No. 3,374,138 to Porter et al. The tire building machine of this patent includes a ring whose only function is to remove the tire band from the building drum. This removal ring is mounted on a pair of overhead I-beams extending in the same direction as the axis of the ring and the building drum. Mounted on these I-beams are rollers that roll on a second pair of I-beams that are perpendicular to the first pair, thus allowing the removal ring to be moved in a horizontal direction perpendicular to the building drum axis. The second pair of I-beams in turn have rollers that roll on a main beam that extends in the same direction as the first pair of I-beams and the axis of the building drum. This allows the removal ring to be moved parallel to the building drum axis. With this rather complex mounting system, the removal ring can be moved axially to a position over an uncured tire, pick up the tire, be moved axially away from the building drum, and then in a direction perpendicular to the drum axis and to a position out of the way of the building drum.
One problem with the tire removal ring of the foregoing Porter patent is that when the ring is moved perpendicular to the drum axis, it moves out from under the main beam that supports the ring and its whole mounting system. This creates a severe moment that can easily cause tilting of the ring and the uncured tire carried thereon. Also, the rollers and other parts of the mounting system are likely to wear badly or break due to the forces created by this moment. This problem could be alleviated by providing a second main beam disposed over the place where the removal ring is to be moved when it is moved out of the way of the building drum. The second pair of I-beams of the ring mounting system would then extend between two main support beams. However, there would still be undesirable forces created while the removal ring with the heavy tire band is moving along this second pair of I-beams between the two main support beams. In view of this, it might be necessary to provide at intermediate positions a third and perhaps a fourth main beam to support the second pair of beams, particularly if the span of this second pair of I-beams is to be a substantial distance. These modifications would not only be expensive but the space requirements for additional supporting beams would complicate the design of an overhead mounted carrying system for taking the tire band from the removal ring and carrying the band to another location in the factory. This is because such a carrying system would have to have a pick-up device that moves into a position parallel to and directly under the additional supporting beams so that it can be aligned with the axis of the tire band that remains at all times aligned with these supporting beams.
Other problems with the ring mounting system shown in the Porter patent is that the removal ring cannot be positioned very accurately over an uncured tire on the building drum, and the ring cannot be held steady while it is picking up an uncured tire from the building drum, or while the tire band is being removed at a place distant from the building drum. These problems arise from the lateral play allowed by the wheel and I-beam type mounting of Porter's tire removal ring and from the fact that there are no positive stopping or holding means for maintaining the wheels stationary on the I-beams while the removal ring is picking up or unloading a tire band.
The lateral play problem could be solved by mounting the removal ring on bearings sliding on cylindrical rails, such as shown in U.S. Pat. Nos. 3,475,254 (Henley) and 3,442,746 (Robertson), mentioned above. However, the mounting system of the Porter patent would require two sets of such sliding bearing and rail arrangements. This would increase the cost and complexity of what is already a fairly complex ring mounting system.
Another system that provides lateral mobility for a transfer ring for tire bands is shown in U.S. Pat. No. 3,532,577 to W. Niclas et al. This patent shows a transfer ring mounted on a single pair of bearings on a single pair of cylindrical rails. The ends of the rails adjacent the building drum are mounted on a carriage that pivots on a vertical shaft, while the other ends of the rails are mounted on a carriage that rides on an arcuate shaft. The object of this apparatus is to provide a transfer ring that can pick up tread belts from any of a plurality of belt building drums. However, this would have several disadvantages if it were to be used as a tire band removal device. First, as with the system of the Porter patent, the rails space requirements for supporting the transfer ring would unduly complicate the design of an overhead mounted carrying system for taking the tire band from the transport ring and carrying the band to another location in the factory. Secondly, the arcuate beam and roller mounted carriage riding on this beam between the tread strip building stations is unnecessarily complicated and expensive. The arcuate beam, in particular, complicates matters, because it would have to be very strong to support the larger sizes of tires as the carriage on this rail moves from one end of the rail to the other. Also, because the beam bows out laterally between its supports, it would be prone to twisting under heavy loads.